Neutral bond in a single phase 480 primary to 240/120 secondary

[Sparky480V]

This is my first time installing a transformer of this type. I know I have to bond my XO in your most common 480 delta stepped down to 120/208 wye but not sure about if I have to bond what is the X3 (or X4, they’re connected) terminal which is where my neutral is landing. Again, this is a 480 SINGLE phase primary stepping down to SINGLE phase 120/240. Please help! Thanks!

 

[augie47]

240/120 systems need to be grounded (250.21) and bonded (250.30) normally with a X2-X3 bonding jumper. (see 250.30 for exceptions )

 

[Sparky480V]

Thanks!

Thanks!

Thanks for the fast answer! I’ve attached pertinent photos even though you answered my question. All I have to do is go from the X3(X4) lug to the bond and it’s all good.

... except for the noalox and torquing of the secondary wires. They’re in there for the sake of the photo and will be taken out before I heat up the transformer and test the secondary voltage.

Again, thank you!

 

[augie47]

Thanks for the fast answer! I’ve attached pertinent photos even though you answered my question. All I have to do is go from the X3(X4) lug to the bond and it’s all good.

... except for the noalox and torquing of the secondary wires. They’re in there for the sake of the photo and will be taken out before I heat up the transformer and test the secondary voltage.

Again, thank you!

Yes a system bonding jumper and a grounding electrode conductor to your grounding terminal
If you are under '17, see 450.10(A)..

 

[texie]

Thanks for the fast answer! I’ve attached pertinent photos even though you answered my question. All I have to do is go from the X3(X4) lug to the bond and it’s all good.

... except for the noalox and torquing of the secondary wires. They’re in there for the sake of the photo and will be taken out before I heat up the transformer and test the secondary voltage.

Again, thank you!

Just to be clear, X1 will be line 1, X4 will be line 2. X2 and X3 tie together and bond. As Augie mentioned, your going to need a grounding electrode as well.

 

[Sparky480V]

Detailed photo

Detailed photo

Just to be clear, X1 will be line 1, X4 will be line 2. X2 and X3 tie together and bond. As Augie mentioned, your going to need a grounding electrode as well.

Thanks for the input. I have it as you explained. Attached is a photo with markups detailing the installation.

 

[infinity]

What size are your secondary conductors and the GEC/SSBJ? The green conductor run with the secondary is the SSBJ (supply side bonding jumper).

Here's a similar transformer with a straight 240 volt secondary. Sorry it's a bit blurry.

 

[LarryFine]

Here's a similar transformer with a straight 240 volt secondary.

View attachment 21913

It sure looks like it has a grounded center tap.

 

[infinity]

It sure looks like it has a grounded center tap.

Yup but no neutral conductor.